But the wolves need not risk injury today. 但是今天的这头狼不需要冒受伤的危险硬闯

169. In the whiteout, the threat is almost impossible to detect,
     在白茫茫的天气中 有危险也几乎不可能察觉到
170. but the musk oxen instinctively retreat to higher ground.
     但是麝牛本能地向高地撤退
171. Forming a defensive ring around their calves, the adults present a barricade that few hunters could breach.
     成牛围成圈以保护它们的小牛, 一般的猎食动物很难突破这层封锁
172. But the wolves need not risk injury today.
     但是今天的这头狼不需要冒受伤的危险硬闯
173. A calf has been left behind in the panic.
     它们在慌乱之中留下一头小牛
174. With each passing day, the sun climbs higher in the sky
     随着时间一天天过去,天上的太阳升得越来越高
175. and its rays strike the Arctic more directly.
     阳光逐渐直射到北极来

来自《行星地球 第一季 第六集 Planet Earth S01E06 冰雪世界》第 172 行